1. Field of Invention
The present invention relates to a paper feeding mechanism, and more particularly, to a paper feeding mechanism capable of realizing fast double-side scanning.
2. Related Art
With the development of the photoelectric technology and the business, a great number of products having multiple functions, such as printers, scanners, copiers, and multi-functional peripherals (MFPs), using optical modules having photosensitive elements, have gradually become daily tools from professional tools due to the low price and good practicability.
Generally, if a single-side scanning apparatus in the prior art is used to scan both pages of a paper, a user has to manually flip the paper after one page has been scanned to proceed the scanning of the other page of the paper. Thus, speed for scanning both pages of a paper is low, and the paper feeding directions of the two pages of the paper may be different due to the careless operation. As for the aforementioned problem, manufacturers have developed a scanning apparatus that realizes double-side scanning, which scans two pages of a paper automatically. Therefore, the user can scan both pages of a piece of paper rapidly, and the problem of different paper feeding directions can be prevented.
Referring to FIG. 1, a scanning apparatus 10 is disclosed in U.S. Pat. No. 5,784,680 “Compact Auto-Document Feeder for an Image Forming Apparatus”, in which a paper P placed on a paper holder 160 is transmitted to a first feeding channel 14 through a pick-up roller 11, a pair of separating rollers 12, and a pair of pull-out rollers 13, so as to scan a first page Pg1 of the paper P in a scanning station 15. After the first page Pg1 is scanned, the paper P is transmitted into a second feeding channel 17 with a pair of assisting rollers 16. As required, if only one side of the paper P needs to be scanned, after the first page Pg1 of the paper P is scanned, the paper P is transmitted to an ejecting tray 18 through the second feeding channel 17. If both sides of the paper P need to be scanned, after the first page Pg1 of the paper P is scanned, the paper P passes through the second feeding channel 17 and is transmitted to a switch-back channel 20 by an ejecting roller 19. The moving direction of the paper P is switched by the switch-back rollers 21, and the paper P is transmitted into the paper-flip channel 22. The paper P is flipped with a second page Pg2 facing the scanning station 15. Then the paper P is transmitted to pass over the scanning region 15, so that the second page Pg2 of the paper P is scanned. After that, the paper P is transmitted to the ejecting tray 18 through the second feeding channel 17.
The double-side scanning apparatus disclosed in U.S. Pat. No. 5,784,680 uses a plurality of roller for transmitting or flipping the paper to be scanned in the double-side scanning apparatus, and these rollers having different motions are driven by at least three driving motors. However, to the manufacturers, the complicated and various control devices require an extremely complex manufacturing flow, and also lead to low assembling and manufacturing speed and high manufacturing cost.
In addition, as for the paper feeding path of the paper of U.S. Pat. No. 5,784,680, a transporting assembly having a plurality of rollers is required to transport the paper moving forward and backward. And in order to ensure the correct scanning sequence of the two pages of the paper to be scanned, after the first page Pg1 of the paper is scanned, the paper has to be fed into the switch-back channel to proceed the scanning of the second page. During the paper is transported and scanned, the next paper can not enter the scanning apparatus, thus the time for the next paper entering the scanning apparatus has to be delayed, and the scanning speed (scan per minute, SPM) is reduced substantially, which cannot satisfy the requirements of high speed and simplicity for current scanning apparatuses.